We went on with our calculations, and on
August 8th, on returning from a visit to John Williams at Barncoose,
we heard that there was a 'run' in Dolcoath, that is a sinking of the
whole mass of rock where it had been set free by the mine excavations:
probably only a few inches, but enough to break the rock much and to
stop the pumps. On Aug. 10th the calculations of our observations
shewed that there was something wrong, and on the 13th I perceived an
anomaly in the form of the knife edge of one pendulum, and of its
agate planes, and suggested cautions for repeating the observations.
We determined at once to repeat them: and as the water was rising in
the mine there was no time to be lost. We again sent the instruments
down, and made observations on the 16th, 17th and 18th. On the 19th I
sent the instruments up, for the water was near our station, and
Sedgwick, Whewell, and I went on a geological expedition to the
Lizard. On our return we met Sheepshanks and the others, and found the
results of the last observations unsatisfactory. The results of
comparing the pendulums were discordant, and the knife edge of the
faulty pendulum had very sensibly altered. We now gave up
observations, with the feeling that our time had been totally lost,
mainly through the fault of the maker of the pendulum (T.
Pages:
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145